Etching method and plasma treatment device

Abstract

In one exemplary embodiment, the etching method includes the following steps: (a) providing a substrate having an etch target film, a patterned polysilicon mask on the etch target film, and a silicon oxide film on the upper surface of the polysilicon mask; (b) removing the silicon oxide film using a first plasma generated by a first processing gas, thereby exposing at least the upper surface of the polysilicon mask; (c) after (b), forming a deposit on the upper surface of the polysilicon mask using a second plasma generated by a second processing gas different from the first processing gas; and (d) after (c), etching the etch target film through the polysilicon mask using a third plasma generated by a third processing gas different from the second processing gas.

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